Field of Invention
This invention relates to integrated circuit fabrication, and particularly relates to a liquid etchant composition, and to an etching process in a capacitor process of DRAM (dynamic random access memory) using the liquid etchant composition.
Description of Related Art
A conventional DRAM cell includes a transistor and a capacitor coupled thereto. In a process for fabricating capacitors of DRAM, lower electrodes of the capacitors, which are made of TiN, are formed in trenches and/or holes previously formed in a poly-Si layer, an aqueous solution of tetramethylammonium hydroxide (TMAH) is used as an etchant to wet-etch and remove the poly-Si layer, and then a capacitor dielectric layer and an upper electrode are formed covering the surfaces of the lower electrodes.
In the above process, a limited etching selectivity of poly-Si to TiN may limit the capacitor height, destroy the structures of the TiN electrodes, or leave behind silicon residuals to cause electrical shorts between the memory cells.